Large eddy simulations of acoustic-flow interaction at an orifice plate
Large eddy simulations of acoustic-flow interaction at an orifice plate
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DOI：
10.1016/j.jsv.2015.02.012
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发表时间：
2015-06
影响因子：
4.7
通讯作者：
E. Alenius;M. Åbom;L. Fuchs
中科院分区：
文献类型：
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作者：
E. Alenius;M. Åbom;L. Fuchs
采用大涡模拟和动态模式分解的方法，研究了圆形和方形通道中具有强偏流的孔板对平面波的散射。声流相互作用的结果表明，在Strouhal数为0.43的情况下，入射声波在方形管道孔口内触发强轴对称流动结构，并与圆形管道孔口内的自持轴对称振荡相互作用。然后，这些结构会产生很强的声音，增加入射波频率处的声能。方形管道中触发的结构比圆形管道中的结构要弱，但比其他频率的波浪触发的结构要强。将散射矩阵与实测值进行比较，两者吻合较好。然而，结果对入流很敏感，其中圆形管道模拟中的自持振荡是轴对称的原状入流的伪影。这说明了使用不受干扰的流入来研究涡旋声音效果的问题，并且在考虑乐器时可能会很感兴趣，因为乐器的目标是获得特定音调的最大放大。进一步说明，在孔板存在声能放大的频率处，流动具有自然不稳定性，这种不稳定性被非轴对称和输入扰动所抑制。
The scattering of plane waves by an orifice plate with a strong bias flow, placed in a circular or square duct, is studied through large eddy simulations and dynamic mode decomposition. The acoustic-flow interaction is illustrated, showing that incoming sound waves at a Strouhal number of 0.43 trigger a strong axisymmetric flow structure in the orifice in the square duct, and interact with a self-sustained axisymmetric oscillation in the circular duct orifice. These structures then generate a strong sound, increasing the acoustic energy at the frequency of the incoming wave. The structure triggered in the square duct is weaker than that present in the circular duct, but stronger than structures triggered by waves at other frequencies. Comparing the scattering matrix with measurements, there is a good agreement. However, the results are found to be sensitive to the inflow, where the self-sustained oscillation in the circular duct simulation is an artefact of an axisymmetric, undisturbed inflow. This illustrates a problem with using an undisturbed inflow for studying vortex-sound effects, and can be of interest when considering musical instruments, where the aim is to get maximum amplification of specific tones. Further, it illustrates that at the frequency where an amplification of acoustic energy is found for the orifice plate, the flow has a natural instability, which is suppressed by non-axisymmetry and incoming disturbances.